Gene therapy is a therapeutic method by which nucleic acid molecules are administered to a subject to supplement or alter genes within the individual. In particular, gene therapy is used for the purpose of the treatment of diseases. Gene therapy is regarded as fundamental to treating genetic diseases, which develop due to mutation or deletion of a gene. Various procedures of introducing a gene encoding a protein into a subject necessary for therapy have been tried, but there are few examples in which satisfactory therapeutic effect is obtained. Thus, there is a need for alternative methods of delivering nucleic acid molecules to subjects for gene therapy applications.